EXHIBIT 99.4

                          AMENDMENT TO RIGHTS AGREEMENT

       AMENDMENT, dated as of December 23, 1999 (this "Amendment"), by and
between SIRIUS SATELLITE RADIO INC., a Delaware corporation (the "Company"), and
CONTINENTAL STOCK TRANSFER & TRUST COMPANY (the "Rights Agent").

                                    RECITALS

       WHEREAS, the Company and the Rights Agent are parties to a Rights
Agreement, dated as of October 22, 1997 (as heretofore amended, the "Rights
Agreement");

       WHEREAS, the Company proposes to issue and sell 2,000,000 shares of its
9.2% Series D Junior Cumulative Convertible Preferred Stock, par value $.001 per
share ("Series D Preferred Stock"), to Blackstone Capital Partners III Merchant
Banking Fund L.P., a Delaware limited partnership ("BCP III") and possibly
certain BCP III affiliates (together with BCP III, the "Purchasers"), pursuant
to a Stock Purchase Agreement, dated as of December 23, 1999 (the "Stock
Purchase Agreement"), by and between the Company and BCP III; and

       WHEREAS, the Company may issue additional shares of Series D Preferred
Stock as dividends on outstanding shares of Series D Preferred Stock in lieu of
paying dividends in cash on such shares;

       WHEREAS, under the terms of the Rights Agreement, unless the Rights
Agreement is amended, the Purchasers would become "Acquiring Persons," as
defined in Section 1(a) of the Rights Agreement, upon the purchase of the Series
D Preferred Stock pursuant to the Stock Purchase Agreement; and

       WHEREAS, the Board of Directors of the Company deems it desirable and in
the best interests of the Company and its stockholders to amend the Rights
Agreement to exclude the Purchasers and any of the Purchasers' Affiliates and
Associates who would otherwise be deemed Beneficial Owners (as defined in the
Rights Agreement) as a result of such transaction from such definition of
"Acquiring Person."

       Accordingly, the parties agree as follows:

       1.     Amendment of Section 1(A). The definition of "Acquiring Person"
set forth in paragraph 1(a) of the Rights Agreement is amended by adding the
following clause at the end of such Section 1(a):

       "; provided, further, that Blackstone Capital Partners III Merchant
       Banking Fund L.P., a Delaware limited partnership (hereinafter referred
       to as "BCP III") and any of the Affiliates or Associates of BCP III that
       would otherwise be deemed to be Beneficial Owners of the Company's 9.2%
       Series D Junior Cumulative Convertible Preferred Stock (hereinafter
       referred to as the "Series D Preferred Stock") (such Affiliates and
       Associates, together with BCP III are hereinafter referred to as the
       "Blackstone Investors") shall not be, or be deemed to be, Acquiring
       Persons solely by reason of the acquisition or




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       beneficial ownership of (w) shares of the Series D Preferred Stock
       pursuant to the Stock Purchase Agreement dated as of December 23, 1999 by
       and between the Company and BCP III, (x) additional shares of Series D
       Preferred Stock pursuant to dividends declared on the Series D Preferred
       Stock (including dividends declared on Series D Preferred Stock issued as
       dividends), (y) Common Shares upon the exercise of conversion rights set
       forth in the Certificate of Designations, Preferences and Relative,
       Participating, Optional and Other Special Rights of the Series D
       Preferred Stock or (z) a number of Common Shares, in addition to those
       referred to in clauses (w), (x) and (y) above, acquired by the Blackstone
       Investors, equal to, collectively, up to one percent (1%) of the total
       number of Common Shares outstanding from time to time."

       2.     Miscellaneous. This Amendment shall be deemed to be a contract
made under the laws of the State of Delaware and for all purposes shall be
governed by and construed in accordance with the laws of such state applicable
to contracts to be made and performed entirely within such state. This Amendment
may be executed in any number of counterparts, each of such counterparts shall
for all purposes be deemed to be an original, and all such counterparts shall
together constitute but one and the same instrument. If any provision, covenant
or restriction of this Amendment is held by a court of competent jurisdiction or
other authority to be invalid, illegal or unenforceable, the remainder of the
terms, provisions, covenants and restrictions of this Amendment shall remain in
full force and effect and shall in no way be effected, impaired or invalidated.

                            (Signature page follows)




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       EXECUTED as of the date set forth above.

                                       SIRIUS SATELLITE RADIO INC.

                                       By:/s/ Patrick L. Donnelly
                                          --------------------------------------
                                          Name:  Patrick L. Donnelly
                                          Title: Senior Vice President,
                                                 General Counsel and Secretary

                                       CONTINENTAL STOCK TRANSFER
                                       & TRUST COMPANY

                                       By:/s/ William F. Seegraber
                                          --------------------------------------
                                          Name:  William F. Seegraber
                                          Title: Vice President